Blow-by gas oil separator

ABSTRACT

A blow-by gas oil separator that can prevent oil discharged into an oil receiving chamber from flowing backward into a cyclone includes: multiple cyclones to which blow-by gas of an internal combustion engine is supplied, each cyclone including, in a lower portion, an oil discharge opening that separates out and discharges oil mist contained in the blow-by gas, and including, in an upper portion, a blow-by gas outlet that allows the blow-by gas to flow out after oil separation; an oil receiving portion opposing the oil discharge openings of the cyclones; a blow-by gas circulation portion in communication with the blow-by gas outlets of the cyclones, and is connected to an air intake passage of the internal combustion engine via a circulation valve; and partition walls in an oil receiving chamber formed by the cyclones and the oil receiving portion to separate adjacent oil discharge openings from each other.

TECHNICAL FIELD

The present invention relates to a blow-by gas oil separator thatincludes multiple cyclones capable of separating out oil mist containedin blow-by gas.

BACKGROUND ART

In an internal combustion engine such as an engine for an automobile,blow-by gas that has leaked from the combustion chamber into thecrankcase is returned to the air intake passage and caused to undergocombustion again in the combustion chamber.

Blow-by gas contains oil mist, which is formed by engine oil or the likethat has been dispersed as microscopic particles, and therefore such oilmist needs to be separated from the blow-by gas before being caused toundergo combustion in the combustion chamber.

The aforementioned blow-by gas oil separator is used in such anapplication.

A conventional blow-by gas oil separator disclosed in Patent Document 1includes: multiple cyclones that are supplied with blow-by gas of aninternal combustion engine, each including, in a lower portion, an oildischarge opening that separates out and discharges oil mist containedin the blow-by gas, and including, in an upper portion, a blow-by gasoutlet that allows the blow-by gas to flow out after oil separation; anoil receiving portion that opposes the oil discharge openings of thecyclones; a blow-by gas circulation portion that is in communicationwith the blow-by gas outlets of the cyclones, and is connected to theair intake passage of the internal combustion engine via a circulationvalve; and an oil receiving chamber formed by the cyclones and the oilreceiving portion.

Due to negative pressure generated in the air intake passage of theinternal combustion engine, blow-by gas is suctioned in and supplied tothe cyclones, and then after oil separation, the blow-by gas issuctioned into the blow-by gas circulation portion through the blow-bygas outlets. The oil that was separated out by the cyclones isdischarged to the oil receiving portion through the oil dischargeopenings due to its own weight.

The oil discharge openings provided in the lower portions of thecyclones and the blow-by gas outlets provided in the upper portions ofthe cyclones are in communication with each other via the interiors ofthe cyclones. Accordingly, negative pressure generated in the air intakepassage is introduced to the oil discharge openings as well.

The magnitude of the negative pressure introduced to an oil dischargeopening increases the closer the blow-by gas outlet in communicationwith that oil discharge opening is located to the circulation valve.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 2009-221857A

SUMMARY OF INVENTION Technical Problem

With the conventional blow-by gas oil separator, there is a risk thatoil in the form of droplets or the like that was discharged into the oilreceiving chamber is suctioned through an oil discharge opening that isnear the circulation valve and is subjected to high negative pressure,and flows backward into a cyclone.

If oil flows backward into a cyclone, that oil is suctioned into theblow-by gas circulation portion through the blow-by gas outlet, and caneasily flow into the air intake passage through the circulation valve.

The present invention was achieved in light of the above-describedcircumstances, and an object thereof is to provide a blow-by gas oilseparator that can prevent oil that was discharged into the oilreceiving chamber from flowing backward into a cyclone.

Solution of Problem

A characteristic configuration of a blow-by gas oil separator accordingto one aspect of the present invention lies in that the blow-by gas oilseparator includes: a plurality of cyclones to which blow-by gas of aninternal combustion engine is supplied, each of the cyclones including,in a lower portion, an oil discharge opening that separates out anddischarges oil mist contained in the blow-by gas, and including, in anupper portion, a blow-by gas outlet that allows the blow-by gas to flowout after oil separation; an oil receiving portion that opposes the oildischarge openings of the plurality of cyclones; a blow-by gascirculation portion that is in communication with the blow-by gasoutlets of the plurality of cyclones, and is connected to an air intakepassage of the internal combustion engine via a circulation valve; andpartition walls that are provided in an oil receiving chamber formed bythe plurality of cyclones and the oil receiving portion, and separateadjacent oil discharge openings from each other.

In the blow-by gas oil separator having this configuration, thepartition walls that separate adjacent oil discharge openings from eachother are provided on the oil receiving chamber.

For this reason, oil in the form of droplets or the like that wasdischarged from the oil discharge openings into the oil receivingportion can be prevented from flowing backward into a cyclone through adifferent oil discharge opening.

Another characteristic configuration of one aspect of the presentinvention lies in that the partition walls are provided so as to beintegrated on a cyclone side, and a gap is formed between lower ends ofthe partition walls and the oil receiving portion.

According to this configuration, the relative positions of the partitionwalls and the cyclones can be easily determined with favorableprecision.

Also, it is easy to cause discharged oil to flow through the gap betweenthe lower ends of the partition walls and the oil receiving portion,toward a drain hole or the like formed in the oil receiving portion, forexample.

Another characteristic configuration of one aspect of the presentinvention lies in that the blow-by gas circulation portion includes aninner bottom portion that is lower with increasing distance from thecirculation valve.

According to this configuration, even if oil that has flowed backwardinto a cyclone is suctioned into the blow-by gas circulation portion andaccumulates, it is possible to cause that oil to flow toward the sidedistant from the circulation valve and prevent that oil from flowinginto the air intake passage through the circulation valve.

Another characteristic configuration of one aspect of the presentinvention lies in that the blow-by gas circulation portion has an innerbottom portion in which the blow-by gas outlets are each formed, and theinner bottom portion is provided with an oil channel along which oil canflow so as to move away from the circulation valve while avoiding theblow-by gas outlets, and a communication channel that can put a terminalside of the oil channel in communication with the oil receiving chamber.

In this configuration as well, even if oil that has flowed backward intoa cyclone is suctioned into the blow-by gas circulation portion andaccumulates, it is possible to cause that oil to flow so as to move awayfrom the circulation valve and prevent that oil from flowing into theair intake passage through the circulation valve.

Also, in the case where the blow-by gas circulation portion has theinner bottom portion in which the blow-by gas outlets are each formed,as in this configuration, there is a risk that oil in the process offlowing along the oil channel flows from a blow-by gas outlet into acyclone, thus reducing the oil separation capability.

For this reason, the blow-by gas oil separator according to thisconfiguration is provided with the oil channel along which oil suctionedinto the blow-by gas circulation portion can flow while avoiding theblow-by gas outlets, and the communication channel that can put theterminal side of the oil channel into communication with the oilreceiving chamber.

Accordingly, oil in the process of flowing along the oil channel can becaused to flow from the communication channel into the oil receivingchamber, without flowing into cyclones, and it is possible to prevent areduction in the oil separation capability of the cyclones.

Another characteristic configuration of one aspect of the presentinvention lies in that the inner bottom portion is provided with aprojection portion that separates one end side of the oil channel in awidth direction from a blow-by gas outlet side.

According to this configuration, when oil flows along the oil channel,the spread of the oil in the channel width direction can be restrictedby the projection portion, and oil in the processing of flowing alongthe oil channel toward the communication channel can be reliablyprevented from flowing into cyclones.

Another characteristic configuration of one aspect of the presentinvention lies in that a receding portion is formed at a terminal sideof the oil channel, the receding portion is deeper than a channelportion on an upstream side of the terminal side of the oil channel, andthe communication channel is open at a bottom portion of the recedingportion.

According to this configuration, it is possible to cause oil flowingalong the oil channel to flow into the receding portion at the terminalside of the oil channel, and cause the oil to flow from thecommunication channel open at the bottom portion of the receding portioninto the oil receiving chamber.

The receding portion is deeper than the channel portion on the upstreamside thereof, and therefore there is little risk that oil that hasaccumulated in the receding portion is suctioned toward the circulationvalve.

Even in the case where the orientation relative to the horizontaldirection is likely to vary, as with an oil separator for an automobilein particular, it is possible to reliably prevent oil from flowing intocyclones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an oil separator.

FIG. 2 is a plan view of the oil separator.

FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2.

FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3 seenin a direction indicated by arrows.

FIG. 5 is a cross-sectional view taken along line V-V in FIG. 3 seen ina direction indicated by arrows.

FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 3 seenin a direction indicated by arrows.

FIG. 7 is a vertical cross-sectional diagram showing an oil separatoraccording to a second embodiment.

FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7seen in a direction indicated by arrows.

FIG. 9 is a vertical cross-sectional diagram showing an oil separatoraccording to a third embodiment.

FIG. 10 is a vertical cross-sectional diagram showing an oil separatoraccording to a fourth embodiment.

FIG. 11 is a vertical cross-sectional diagram showing an oil separatoraccording to a fifth embodiment.

FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 11seen in a direction indicated by arrows.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings.

First Embodiment

FIGS. 1 to 6 show a cyclone-type blow-by gas oil separator according tothe present invention, which is for mounting inside a cylinder headcover (not shown) or the like of an internal combustion engine such asan engine for an automobile.

In the oil separator A, internal combustion engine blow-by gas thatflows from the crankcase (not shown) into the cylinder head cover issupplied to cyclones B by being suctioned by negative pressure generatedin an air intake passage (not shown) in accompaniment with an air intakeoperation of the internal combustion engine, and oil mist contained inthe blow-by gas is removed by centrifugal separation.

After the oil mist has been removed, the blow-by gas is returned to theair intake passage of the internal combustion engine via a circulationvalve (not shown) such as a PCV valve (Positive Crankcase Ventilationvalve), and then subjected to combustion again in the combustionchamber.

As shown in FIG. 3, the oil separator A includes, inside a resin housing1, multiple (four in the present embodiment) cyclones B to which blow-bygas is supplied, an oil receiving chamber 2 that receives oil separatedout by the cyclones B, and a blow-by gas circulation chamber (blow-bygas circulation portion) 3 that is connected to the air intake passageof the internal combustion engine via the circulation valve.

The cyclones B each include, in a lower portion, an oil dischargeopening 4 that separates out oil mist contained in blow-by gas anddischarges the oil mist using the weight thereof, and include, in anupper portion, a blow-by gas outlet 5 that allows the blow-by gas toflow out after oil separation.

The oil receiving chamber 2 is formed between the four cyclones B and anoil receiving portion 6 that opposes the oil discharge openings 4, andis configured so as to collect oil that is discharged from the oildischarge openings 4, and return the oil to the inside of the enginethrough a drain pipe 7.

The blow-by gas outlets 5 are each in communication with the blow-by gascirculation chamber 3, and are configured so as to collect the blow-bygas flowing in through the blow-by gas outlets 5 after oil separation,and return the blow-by gas from a gas discharge pipe 8 to the air intakepassage of the internal combustion engine via the circulation valve.

As shown in FIGS. 1 to 3, the housing 1 is assembled by fitting a lowercase 1 a and an intermediate case 1 b to an upper case 1 c and a lidcase 1 d in the vertical direction.

The space formed between the lower case 1 a and the intermediate case 1b is partitioned into the oil receiving chamber 2 and a gas introductionchamber 9 into which blow-by gas inside the cylinder head cover isintroduced through a gas introducing opening 9 a.

As shown in FIG. 5, a straightening chamber 10, which straightens theflow of blow-by gas before flowing into the cyclones B, and a blow-bygas inflow passage 10 a, which allows blow-by gas to flow from the gasintroduction chamber 9 into the straightening chamber 10, are formedbetween the intermediate case 1 b and the upper case 1 c.

The space between the upper case 1 c and the lid case 1 d forms theblow-by gas circulation chamber 3 as shown in FIG. 4.

The drain pipe 7, by which oil collected in the oil receiving chamber 2is returned to the inside of the engine, is connected to the lower case1 a.

The oil receiving portion 6 is formed by the bottom plate portion of thelower case 1 a, and is inclined such that oil flows toward the drainpipe 7 due to its own weight.

As shown in FIGS. 3 and 5, an oil receiving chamber upper wall 2 a,which separates the straightening chamber 10 and the oil receivingchamber 2 in the vertical direction, and the four cyclones B thatpenetrate the oil receiving chamber upper wall 2 a in the verticaldirection are formed so as to be integrated in the intermediate case 1b.

As shown in FIGS. 3 and 5, the cyclones B each include a conical tubewall portion 12 whose inner diameter decreases as it extends downward,and a circular tube wall portion 11 whose inner diameter is constant andthat extends upward from the upper edge of the conical tube wall portion12, and the conical tube wall portion 12 and the circular tube wallportion 11 are integrated about a tube axis X that extends in thevertical direction.

The four cyclones B are arranged side-by-side in a straight line withthe positions of their tube axes X at equal intervals in a plan view,and are aligned such that the circular tube wall portions 11 areconnected to each other in an integrated manner.

The circular tube wall portions 11 are provided so as to protrude fromthe oil receiving chamber upper wall 2 a into the straightening chamber10, and a blow-by gas supply opening 11 a, which allows blow-by gas inthe straightening chamber 10 to flow in from a direction tangential tothe inner side of the circular tube wall portion 11, is formed as a slitin each of the circular tube wall portions 11.

The conical tube wall portions 12 are provided so as to protrude fromthe oil receiving chamber upper wall 2 a into the oil receiving chamber2, and the lower end openings of the conical tube wall portions 12function as the oil discharge openings 4.

As shown in FIGS. 3 and 4, the upper case 1 c includes a distributionchamber lower wall 3 a that separates the blow-by gas circulationchamber 3 and the straightening chamber 10 in the vertical direction,and the blow-by gas outlets 5 are formed in the distribution chamberlower wall 3 a.

Accordingly, the blow-by gas circulation chamber 3 has an inner bottomportion 16 in which the blow-by gas outlets 5 are each formed. The upperend portions of the circular tube wall portions 11 are fitted into andfixed to the lower surface side of the distribution chamber lower wall 3a.

Circular tube portions 13 that form the blow-by gas outlets 5 are formedso as to be integrated with the lower surface side of the distributionchamber lower wall 3 a. The circular tube portions 13 are provided so asto coaxially enter the corresponding cyclones B with a gap in thediameter direction from the inner sides of the circular tube wallportions 11.

The gas discharge pipe 8, which is connected to the air intake passageof the internal combustion engine via the circulation valve, is providedin the lid case 1 d.

As shown in FIG. 4, the gas discharge pipe 8 is provided so as to be incommunication with the interior of the blow-by gas circulation chamber 3on one end side in the alignment direction of the blow-by gas outlets 5(on the side distant from the blow-by gas inflow passage 10 a).

The following describes operations of the oil separator A.

Blow-by gas inside the cylinder head cover is introduced into the gasintroduction chamber 9 by being suctioned through the gas introducingopening 9 a due to negative pressure generated in the air intake passagein accompaniment with an air intake operation of the internal combustionengine.

The blow-by gas introduced into the gas introduction chamber 9 flowsinto the straightening chamber 10 through the blow-by gas inflow passage10 a, and then flows from the blow-by gas supply openings 11 a into thecircular tube wall portions 11.

Oil mist contained in the blow-by gas that flowed into the circular tubewall portions 11 undergoes coagulative separation into droplets of oildue to centrifugal force that accompanies circulation about the tubeaxis (circular tube portions 13) X.

The oil separated out in the form of droplets by the cyclones B thenfalls through the oil discharge openings 4 into the oil receivingchamber 2 and is collected in the oil receiving portion 6, and is thenreturned to the inside of the engine through the drain pipe 7.

After the oil mist has been separated out, the blow-by gas is suctionedthrough the circular tube portions 13 into the blow-by gas circulationchamber 3 via the blow-by gas outlets 5, and then flows back through thegas discharge pipe 8 to the combustion chamber via the air intakepassage.

The oil discharge openings 4 provided in the cyclones B are incommunication with the blow-by gas outlets 5 inside the cyclones B. Forthis reason, negative pressure generated in the air intake passage actson the oil discharge openings 4 as well, and there is a risk thatdroplets of oil discharged into the oil receiving chamber 2 aresuctioned through the oil discharge openings 4, travel inside thecyclones B, and flow backward into the blow-by gas circulation chamber3.

The magnitude of the negative pressure acting on an oil dischargeopening 4 of a cyclone B increases the closer the blow-by gas outlet 5in communication with the oil discharge opening 4 is arranged to theentrance of the gas discharge pipe 8 (the downstream side in thedirection of the flow of blow-by gas toward the air intake passage).

For this reason, droplets of oil discharged from one oil dischargeopening 4 into the oil receiving chamber 2 need to be prevented frombeing suctioned through an oil discharge opening 4 different from thatone oil discharge opening 4, that is to say, through the oil dischargeopening 4 of a cyclone B that is arranged farther downstream, in thedirection of the flow of blow-by gas toward the gas discharge pipe 8,than the cyclone B that includes that one oil discharge opening 4.

In order to prevent this suctioning of oil, band plate-shaped partitionwalls 14 are provided in order to, by separating adjacent oil dischargeopenings 4 from each other, prevent the suctioning of droplets of oilthrough oil discharge openings 4 on which high negative pressure easilyacts.

The partition walls 14 are provided on the cyclone B side, that is tosay, so as to be integrated with the intermediate case 1 b, betweenrespective pairs of adjacent conical tube wall portions 12, and extendin a straight line so as to traverse the interior of the oil receivingchamber 2 in the direction orthogonal to the alignment direction of thecyclones B.

A slit-shaped gap 15 that extends along the oil receiving surface of theoil receiving portion 6 is formed between the lower ends of thepartition walls 14 and the oil receiving portion 6.

If oil that has been discharged to the oil receiving chamber 2 issuctioned through an oil discharge opening 4 and flows backward into acyclone B, that oil flows into the blow-by gas circulation chamber 3along with blow-by gas and accumulates.

Also, if oil mist is not completely separated out by the cyclones B andremains in blow-by gas that is suctioned into the blow-by gascirculation chamber 3, such oil mist coagulates and remains inside theblow-by gas circulation chamber 3.

For this reason, the blow-by gas circulation chamber 3 is provided in anorientation in which the upper surface of the distribution chamber lowerwall 3 a, which forms the inner bottom portion 16 of the blow-by gascirculation chamber 3, is inclined relative to the horizontal directionso as to become lower with increasing distance from the circulationvalve, that is to say with increasing distance from the entrance of thegas discharge pipe 8, such that oil that has accumulated therein can bedischarged to the oil receiving chamber 2.

As shown in FIG. 4, the inner bottom portion 16 is provided with an oilchannel 17 along which oil can flow due to its own weight so as to moveaway from the circulation valve, that is to say move away from theentrance of the gas discharge pipe 8, while avoiding the blow-by gasoutlets 5. A communication channel 18, which can put the oil channel 17into communication with the oil receiving chamber 2, is open at theterminal side of the oil channel 17. The communication channel 18 isformed by one of the circular tube portions 13.

The oil channel 17 is formed as a channel that is sandwiched between aside wall portion 19 of the upper case 1 c that surrounds the blow-bygas circulation chamber 3 and a projection portion 20 that projects fromthe inner bottom portion 16 and extends along the alignment direction ofthe blow-by gas outlets 5 at a position separated from them.

The projection portion 20 is provided so as to extend in a continuousmanner from a position in the vicinity of and below the entrance of thegas discharge pipe 8 to the blow-by gas outlet 5 located the farthestfrom the entrance of the gas discharge pipe 8, and separates one endside of the oil channel 17 in the width direction from the blow-by gasoutlet 5 side.

Among the circular tube portions 13 of the cyclones B, the communicationchannel 18 is formed by the circular tube portion 13 that is incommunication with the blow-by gas outlet 5 at the farthest positionfrom the circulation valve, that is to say the farthest position fromthe entrance of the gas discharge pipe 8.

Accordingly, oil that has flowed from the oil channel 17 into thecommunication channel 18 travels through the interior of the cyclone Band is discharged from the oil discharge opening 4 into the oilreceiving chamber 2.

Second Embodiment

FIGS. 7 and 8 show another embodiment of the present invention.

In the present embodiment, in order to prevent droplets of oildischarged from one oil discharge opening 4 into the oil receivingchamber 2 from being suctioned through an oil discharge opening 4different from that one oil discharge opening 4, tube-shaped partitionwalls 14 are provided instead of the band plate-shaped partition walls14 described in the first embodiment. The tube-shaped partition walls 14extend from the lower end sides of the circular tube wall portions 11that constitute the cyclones B, in the shape of cylinders that surroundthe conical tube wall portions 12, and separate adjacent oil dischargeopenings 4 from each other.

A gap 15 is formed between the lower ends of the tube-shaped partitionwalls 14 and the oil receiving portion 6, so as to separate the lowerends of the tube-shaped partition walls 14 from the oil receivingportion 6.

Other aspects of the configuration are the same as in the firstembodiment.

Third Embodiment

FIG. 9 shows another embodiment of the present invention.

In the present embodiment, in order to prevent droplets of oildischarged from one oil discharge opening 4 into the oil receivingchamber 2 from being suctioned through an oil discharge opening 4different from that one oil discharge opening 4, ring-shaped partitionwalls 14 are provided instead of the tube-shaped partition walls 14described in the second embodiment. The ring-shaped partition walls 14are obtained by extending the lower ends of the conical tube wallportions 12 that constitute the cyclones B toward the oil receivingportion 6, and separate adjacent oil discharge openings 4 from eachother.

Other aspects of the configuration are the same as in the secondembodiment.

Fourth Embodiment

FIG. 10 shows another embodiment of the present invention.

In the present embodiment, in order to prevent droplets of oildischarged from one oil discharge opening 4 into the oil receivingchamber 2 from being suctioned through an oil discharge opening 4different from that one oil discharge opening 4, band plate-shapedpartition walls 14 are provided instead of the partition walls 14described in the first embodiment that are provided so as to beintegrated with the intermediate case 1 b. The band plate-shapedpartition walls 14 are provided so as to be integrated with the lowercase 1 a that forms the oil receiving chamber 2, and separate adjacentoil discharge openings 4 from each other.

The partition walls 14 are provided between respective pairs of adjacentconical tube wall portions 12, and extend in a straight line so as totraverse the interior of the oil receiving chamber 2 in the directionorthogonal to the alignment direction of the cyclones B.

Arc-shaped through-holes 14 a, for example, are formed in portions ofthe partition walls 14 that rise up from the oil receiving portion 6, soas to not hinder the flow of oil toward the drain pipe 7.

Other aspects of the configuration are the same as in the firstembodiment.

Fifth Embodiment

FIGS. 11 and 12 show another embodiment of the present invention.

In the present embodiment, a circular receding portion 21 is formed atthe terminal side of the oil channel 17 illustrated in the firstembodiment, and is deeper than the channel portion on the upstream sideof the terminal side of the oil channel 17.

Among the circular tube portions 13 of the cyclones B, the recedingportion 21 is formed so as to be coaxial with the circular tube portion13 that is in communication with the blow-by gas outlet 5 at thefarthest position from the circulation valve, that is to say thefarthest position from the entrance of the gas discharge pipe 8, and theblow-by gas outlet 5 that forms the communication channel 18 is formedin the bottom portion of the receding portion 21.

Other aspects of the configuration are the same as in the firstembodiment.

Other Embodiments

1. The oil separator according to the present invention may be providedoutside of the cylinder head cover.

2. The oil separator according to the present invention can be mountedin various types of internal combustion engines other than an engine foran automobile.

REFERENCE SIGNS LIST

2: oil receiving chamber

3: blow-by gas circulation portion (blow-by gas circulation chamber)

4: oil discharge opening

5: blow-by gas outlet

6: oil receiving portion

14: partition wall

15: gap

16: inner bottom portion

17: oil channel

18: communication channel

20: projection portion

21: receding portion

B: cyclone

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. A blow-by gas oil separator comprising: a plurality ofcyclones to which blow-by gas of an internal combustion engine issupplied, each of the cyclones including, in a lower portion, an oildischarge opening that separates out and discharges oil mist containedin the blow-by gas, and including, in an upper portion, a blow-by gasoutlet that allows the blow-by gas to flow out after oil separation; anoil receiving portion that opposes the oil discharge openings of theplurality of cyclones; a blow-by gas circulation portion that is incommunication with the blow-by gas outlets of the plurality of cyclones,and is connected to an air intake passage of the internal combustionengine via a circulation valve; and partition walls that are provided inan oil receiving chamber formed by the plurality of cyclones and the oilreceiving portion, and separate adjacent oil discharge openings fromeach other, wherein the partition walls are provided so as to beintegrated with the cyclones, and a gap is formed between lower ends ofthe partition walls and the oil receiving portion.
 8. The blow-by gasoil separator according to claim 7, wherein the blow-by gas circulationportion includes an inner bottom portion that is lower with increasingdistance from the circulation valve.
 9. The blow-by gas oil separatoraccording to claim 7, wherein the blow-by gas circulation portion has aninner bottom portion in which the blow-by gas outlets are each formed,and the inner bottom portion is provided with an oil channel along whichoil can flow so as to move away from the circulation valve whileavoiding the blow-by gas outlets, and a communication channel that canput a terminal side of the oil channel in communication with the oilreceiving chamber.
 10. The blow-by gas oil separator according to claim9, wherein the inner bottom portion is provided with a projectionportion that separates one end side of the oil channel in a widthdirection from a blow-by gas outlet side.
 11. The blow-by gas oilseparator according to claim 9, wherein a receding portion is formed ata terminal side of the oil channel, the receding portion is deeper thana channel portion on an upstream side of the terminal side of the oilchannel, and the communication channel is open at a bottom portion ofthe receding portion.